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The Grand Paris Express project, creation of a new transport network, provides a large amount of field data from a wide geotechnical campaign with in situ and laboratory tests. The results about the Ypresian plastic clay of the Paris sedimentary basin, obtained from a section of 5.2 km on the future subway line 15, are compiled and analysed in this paper. The geotechnical variability of this specific soil is assessed through the coefficients of variation ( C O V) of four groups of soil parameters namely: the clay index properties (water content, plasticity index, clay content), the shear strength (effective friction angle and cohesion, undrained shear strength), the deformation modulus, and the coefficient of earth pressure at rest K 0 . The C O V derived from vertical spatial variability is compared to the results of a 8-dimensional multivariate normal distribution which correlates the measured parameters at the same depth. The marginal distribution of a soil parameter given other geotechnical parameters reduces systematically the C O V. The variability of the effective friction angle was derived from a special statistical analysis of the failure stress points. This paper concludes with specific guidelines on the typical C O V and means values for different geotechnical parameters that may supply further reliability analysis. [ABSTRACT FROM AUTHOR]

• Plastic clay can be modelled in drained conditions. • FEM-3D calculations are appropriate to reproduce on site recorded displacements. • SRM underestimates the props loads. As part of the Grand Paris Express project, Fort d'Issy-Vanves-Clamart (FIVC) is one of the 60 new metro stations involving a 32 m deep excavation in layered soils made of limestones and clays. The support system was subject to a comprehensive monitoring program to assess the behavior of the soil and the structure during the works [22]. It comprises wall displacements using inclinometers, bending moments using fiber optic, struts and beams loads using strain gauges and earth pressures at the soil/wall interface using pressure cells. The present paper presents the back analysis done using Finite Elements Models (FEM) in 2D and 3D and, the subgrade reaction method (SRM). The results depict a great consistency between FEM and SRM in terms of reproducing, at the same accuracy level, the wall displacements and bending moments. However, the earth pressure redistribution behind the wall and the props loads are significantly underestimated by SRM (40%) especially for deep excavations. Only FEM can reproduce the measurements since arching effect is allowed within the soil. The present back analysis provides adjustment to the input soil parameters in compliance with their variation range. The resulting set of parameters could be used for an optimization purpose in future designs of deep excavations in similar ground conditions. [ABSTRACT FROM AUTHOR]